Section 001-375-4 - Definition of "Unsafe and Insufficient"A dam or reservoir shall be declared to be "unsafe" or "insufficient" if the Inspector of Dams, after utilizing all available data and testimony and making appropriate calculations using known values or reasonable assumptions, finds that the dam or reservoir does not meet minimum performance criteria appropriate to the facility. The types of performance features that should be evaluated are listed below:
A. Forces acting on the dam and evidence of horizontal translation that suggests there is too much force acting at any time against the facility;B. Evidence of large total or differential deformation;C. Evidence of slumps or bulges on the faces of the dam; an end-of-construction or steady state factor of safety against shear sliding and the factor of safety under conditions of reservoir drawdown and during appropriate earthquake loading;D. Evidence that the phreatic surface within the dam during the full reservoir condition exists on the downstream face of the dam except through properly designed drains; evidence of bulges, seeps, or soft zones on the downstream face of the dam or on the immediate. abutments; evaluation of the effective stress within the dam;E. Evidence that the dam is experiencing internal erosion of dam material or that the dam abutments or foundation could be subject to piping; an evaluation of internal drain design; an evaluation of seepage gradient within the dam;F. An evaluation of the quantity and quality of seepage through the damG. An evaluation of whether a dam or reservoir is safe from runoff overtopping that could wash out the containment structure. In making this evaluation, the inspector shall consider whether the dam can safely sustain overtopping by the appropriate design storm, and if not, whether an emergency spillway is present. In appropriate cases where it is determined that an emergency spillway should be present, and only one spillway exists, the principal spillway may be considered to serve as an emergency spillway, provided that the principal spillway is large enough so that it cannot be blocked by driftwood and other floating or suspended debris. For each class of structure identified in paragraphs (1), (2) and (3), the inspector shall consider whether an emergency spillway is able to transmit without erosion,, or whether the dam can retain its integrity during overtopping, a storm of the frequency specified (1) For class "a" structures, which are located in rural, agricultural, or urban areas dedicated to remain in flood tolerant usages where failure may only damage non-residential buildings, agricultural land, floodplains, or township and country roads: 25-year storm or flood;(2) For Class "b" structures, which are located in predominantly rural or agricultural areas where failure may damage homes, industrial or commercial buildings, highways or railroads, or where failure may cause interruption of use or service of utilities: 100-year storm or flood;(3) For Class "c" structures, where failure may cause loss of life: maximum probable flood.H. An evaluation of the minimum freeboard during the reservoir levels that will prevail during the appropriate design storm or flood described in sub-section G above; in a reservoir where landsliding of earth or rack into the reservoir is possible, the potential for wave generation and wave run-up on the dam;I. Evidence of holes or burrows that could render the dam unsafe;J. Consequences of inappropriate dam placement;K. An earthdam shall not be covered by brush, shrubs, or trees;L. The mechanical facilities that provide control of the water levels in a reservoir shall be in good working order.01-001 C.M.R. ch. 375, § 4